A liquid crystal display (LCD) includes a liquid crystal panel, and the liquid crystal panel includes lower and upper substrates facing each other with a liquid crystal layer therebetween. The liquid crystal layer has optical anisotropy and polarizability.
Electric field generating electrodes are formed respectively on facing surfaces of the lower and upper substrates. The alignment direction of liquid crystal molecules changes according to a voltage difference between the electric field generating electrodes, and various images are displayed through a change in a light transmittance due to the change in the alignment direction.
An active matrix mode liquid crystal display that independently controls a plurality of pixels defined in a liquid crystal panel by using switching devices is being widely used. A liquid crystal display using a thin film transistor (TFT) as the switching device is the well-known TFT-LCD.
A manufacturing procedure for the LCD can be separated into a substrate fabricating process, a cell fabricating process, and a module process.
The substrate fabricating process is subdivided into a TFT fabricating process and a color filter fabricating process using a cleaned glass substrate.
The TFT fabrication process forms a plurality of TFTs and pixel electrodes on a lower substrate. The color filter fabricating process forms a common electrode on an upper substrate (on which a black matrix is formed) by forming an R/G/B color filter layer on the upper substrate by using a colorant.
The cell process is a process of fabricating a LCD cell by dispersing spacers between the above lower and upper substrates, assembling the substrates, and then injecting liquid crystal between the assembled substrates.
The module process is a process of fabricating a module by fabricating a signal processing circuit and then connecting a TFT-LCD panel to the signal processing circuit.
In the substrate fabricating process, individual processes such as photolithography, etching, and cleaning are performed to pattern a thin film deposited on a substrate. The individual processes may require a plurality of task repetitions.
The processes are performed such that the thin film is etched after patterning a photoresist on a substrate on which the thin film is deposited, and then the thin film is patterned by removing the photoresist.
Specifically, the photoresist pattering process is a basic process of accurately pattering the thin film, in the LCD manufacturing process.
The photoresist pattering process is performed such that the photoresist is coated on a substrate, the coated photoresist is aligned with respect to a mask and exposed to an ultraviolet (UV) light source. The exposed photoresist and the non-exposed photoresist are differently developed.
At this time, an example of a device for coating the photoresist on the substrate is a photoresist nozzle used in a spin coating method. A photoresist nozzle is fixed over a substrate and dispenses a photoresist on the substrate, and the dispensed photoresist is coated on the whole upper surface of the substrate by the rapid rotation of the substrate.
However, the spin coating method has the following drawbacks.
First, with an increase in the size of an LCD, it becomes more difficult to rapidly rotate a substrate.
Second, the spin coating method causes the upper center and edge portions of the substrate to be more thickly coated with a photoresist than the other upper portions of the substrate, thereby resulting in a non-uniform coating of the substrate.
With an increase in the size of the substrate, a problem of the non-uniform coating becomes more serious.